Dual pressure welding machine

ABSTRACT

A dual pressure welding machine employing a magnetic connection to secure a first and higher pressure to cold flow or mechanically separate the insulation from a wire to be welded from the interfaces between an electrode, the wire and a terminal to which the wire is to be welded. When the magnetic connection is broken a second and lower welding pressure is applied from the electrode to the wire and terminal by means of a spring which may be a constant-force spring applying the same pressure regardless of its extended length or which may be an extension spring whose pressure increases with its extended length so that the welding pressure may be adjusted. The machine includes a pair of carriages connected together by the magnetic connection and the spring, with one carriage carrying the electrodes and the other moveable by either a pneumatic or manual operator.

[73] Assignee:

United States Patent Conley [54] DUAL PRESSURE WELDING MACHINE [72]Inventor: I Larry R. Conley, Simi, Calif.

Accra-Point Arrays Corp., Chatsworth, Calif.

22 Filed: June 16, 1970 [21] Appl.No.: 46,770

[52] US. Cl ..2l9/78, 219/86 [51] Int. Cl. .B2 3k 9/28,B23k 11/10 [58]Field of Search ..2l9/78, 86

[56] References Cited UNITED sTATEs PATENTS 3,436,513 4/1969 Harris..2l9/86 X 3,342,972 9/1967 Penberg 3,252,203 5/1966 Alberts et al2,872,564 2/1959 Du Fresne et a 3,100,831 8/1963 Wakeley 2,996,6038/1961 Stolz et a].

9/1966 Helms 1 May'2, 1972 Primary Examiner-J. V. Truhe AssistantExaminer-Hugh D. Jaeger Attorney-Fulwider, Patton, Rieber. Lee & Utecht[57] ABSTRACT A dual pressure welding machine employing a magneticconnection to secure a first and higher pressure to cold flow ormechanically separate the insulation from a wire to be welded from theinterfaces between an electrode. the wire and a terminal to which thewire is to be welded. When the magnetic connection is broken a secondand lower welding pressure is applied from the electrode to the wire andterminal by means of a spring which may be a constant-force springapplying the same pressure regardless of its extended length or whichmay be an extension spring whose pressure increases with its extendedlength so that the welding pressure may be adjusted. The machineincludes a pair of carriages connected together by the magneticconnection and the spring, with one carriage carrying the electrodes andthe other moveable by either a pneumatic or manual operator.

23 Claims, 3 Drawing Figures w 745mm) PATENTEDMAY 2mm SHEET 1 BF 2 2 M mC w o oa i P W lull/III,

VIII/[Iii INVEN 10R. [422 260M! Jrroewns PATENTEDMM 2 I972 SHEET 2 [1F 21 DUAL PRESSURE WELDING MACHINE BACKGROUND OF THE INVENTION pressuresufficient to so cold flow the insulation is too great for satisfactorywelding of the wire to the terminal part.

The present invention'provides a simple, inexpensive, dualpressuremachine employing a magnetic connection between a pair of relativelyrnoveable carriages for the initial high pressure and a springconnection between the carriages for applying the welding pressure afterthe magnetic connection has been broken.

' .EUMMARYOF THE INVENTION The "weldin'ginachineof thepresent inventionemploys a pair of carriages whichare moveable together or relative toeach othenwith a first carriage carrying a welding electrode andthesecond carriage' being connected to operating means. The twocarriages are connected together by magnetic means for common movementas a unit to apply an initial, relatively high pressure from the weldingelectrode and the carriages are connected together by spring meanspennitting relative movement therebetween whenthe magnetic connection isbroken to apply a lesser welding pressure from the electrode.

The magnetic connection maybeprovided by a permanent magnet mounted onone of the carriages and a magnetic bar mounted on the othercarriage'and bridging the pole pieces of the magnet. i

The spring means connecting the carriages may be a constant-force springapplying the same pressure to the electrode regardless of the length towhich the spring may be extended whereby different length parts may bewelded with a constant weldingpressure without changing the machine. Thespring may also" be a conventional extension spring whose pressureincreases as itslength increases so' that the welding pressure may bechanged by adjusting the travel ofthe second carriage relative to thefirst carriage; for this purpose adjustable stop means are provided forlimitingthe movement of the second carriage.

A control switch is positioned to beoperated by the second carriage nearthe end of its movement and the control switch operatormay beeitherffixed or adjustable. The control switch controlsthe applicationof power to the welding electrodes.

The operator for 'the'f'second carriage for effecting movement thereofin the 'welding'direction may be a pneumatic operator, a manualoperatoror' any other desired means. The second'carriage is returnedaway from'welding position by a retu'rn fspi-ing whicli'ther'ebyreengages the'magnetic connections betweenthe carriages.

Whilethe welding machine inthis'invention is of generalapplication, thearrangement of pressures provided by the magneticandspring'connectionsbetween the carriages is particularly adapted to the welding of aninsulated wire to a terminal in which the initial highpressure'through'the magnetic connection cold flows or separates'theinsulation from the interfaces between the'wire'andtheelectrodeandterminal to make metallic contact therebe'tween. The secondand lowerpressure from the springconnection is applied to the wire and theterminal as the current is sent therethrough to make the weldf'ln thisparticular application it has been foundthat the pressure 'desired' foran efficient "weld is insufficient to mechanicallyseparatethefinsulating covering on the wire, while a press'urewhichissuff cient to separate the insulation is too high to produce'hi'gh'quality welds. The machine of the present invention s'olves thisdifficulty with the initial high pressur for mechanical insulationseparation supplied through the magneticcor'inection which, when broken,lowers the pressure on the electrode to that supplied by the springconnection between the carriages.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view, partly diagrammaticand partly in vertical section, of a dual-presure welding machineaccording to the present invention.

FIG. 2 is a partial view showing a welding machine according to thepresent invention employing a mechanical operator.

FIG. 3 is a partial view of a further modified form of the inventionusing a conventional coil spring and having an adjustable stop and anadjustable switch operator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The welding machine accordingto the present invention, in the specific examplification shown in FIG.1, comprises a stationary base 11 suitably supported by means not shown,and having attached to, and depending therefrom an air cylinder 12having a moveable piston head 13 sealed therein and connected to apiston rod 14. The upper end of chamber 12 is fed by air undercompression through tubing 15 and a two-way valve 16 having a vent 17 toatmosphere. The base 11 hasa opening 18 therethrough in which isdisposed an insulating bushing 19 carrying a headed sleeve 21 thereinthrough which extends a lower electrode22 which is connected by a line23 to a welding current power supply 24. The power supply has suitablewelding current controltherein which is actuated by the closing of acontrol circuit A,B by a normally open switch 25 having a pivotedoperating arm 26, the switch 25 being mounted adjacent the upper surfaceof the base 11.

Extending upwardly from the base 11' in spaced, parallel relation are apair of precision ground posts or shafts 27 and '28 joined adjacenttheir tops by a cross head 29. Mounted on v 34 and held thereto bylocking nut 35. Surrounding the rod 14 within the base 11 is a bearingbushing 36 and between a washer 37 engaging the nut 35 and a washer 38eng' ging the bushing 36 is a compression return spring 39 biasing elower carriage 32 upwardly into non-welding position. A plug or bracket41 extends to one side of the lower carriage 32 to support the rotatablespindle 42 of a coiled, constant-force spring 43 which has no springconstant and applies the same pressure regardless of the length to whichit is extended. Such springs are known and available on the commercialmarket. An L- shaped bracket 61 is mounted to one side of the uppercarriage 31 by a stud 62 to which is also attached the power conductor63 from the weld power supply. The free end of the constant-force spring43 is secured to the bracket 61 by a rivet 64.

Upon the upper surface of the lower carriage 32, adjacent the centerthereof, is mounted a permanent magnet 44 as by a stud 45. Beneath theupper carriage 31 is mounted a magnetic bar 46 which is spaced from thecarriage by a spacing bushing 47 and has a flat headed screw 48 passingtherethrough and through the carriage and held by a nut 49. Thecross-bar 29 has an opening 51 therethrough receiving the nut 49 so thatthe upper carriage 31 stops upwardly by direct engagement with thecrossbar. The spring 39 is recessed into the basel 1 so that the lowercarriage 32 bottoms directly against the top surface of the base. Themagnetic bar 46 is positioned so that it will engage both the polepieces of the permanent magnet 44 to magnetically connect the carriages31 and 32 together, thereby securing the initial high pressure whichcold flows or mechani-cally separates the insulation from the wirecontact surfaces.

An arm 52 is mounted in a side opening of the upper cararm 52 supports amoveable electrode 54 which is hollow to feed the insulated wire 55 tobe welded through the electrode where it loops past its bottom weldingsurface 56. A terminal pin 57, mounted in an insulating terminal board58 with its head 59 thereagainst, is disposed between the lowerelectrode 22 and the upper electrode 54 so that the wire 55 will bepressed against the head 59 of the terminal pin by the welding surface56. After the insulation has been moved out of the way by the initialhighpressure, a direct metallic contact is made between the surface 56,the surface of the metallic wire and the head of the terminal pin. Byway of example only, the wire 55 may be of nickel with its insulatingcoating a fluorocarbon resin such as Teflon. The terminal 57 may be ofnickel or stainless steel.

An optional feature of the construction of FIG. 1 lies in a dual dashpotsystem represented by the dashpots 65 and 66 whose pistons are bothconnected to the lower carriage 32, the dashpot 65 by its rod 67 to aside lug 68 and the dashpot 66 by its rod 69 to the spring spindle 42.The dashpots 65 and 66 serve to dampen out any mechanical transientswhich may occur when the magnet 44 separates from and engages themagnetic bar 46 and the dashpots 65 and 66 may delay in both directionsfor maximum effect.

The operation of the welding machine of FIG. 1 is as follows:

The parts, in their upper, non-welding position, are positioned with theupper carriage 31 pressed against the cross-bar 29 by the return spring39 and with the magnet 44 in connecting engagement with magnet bar 46.In the figure, the carriage 31 is shown in a position slightly below thecross-bar prior to reaching and being pressed thereagainst. The coveredwire 55 is fed through the electrode 54 and a terminal pin 57in aterminal board is placed between the electrodes 22 and 54 so as to weldthe wire 55 to its head 59. Pressure is admitted to the top of thecylinder 12 through valve 16 and the lower carriage 32 is moveddownwardly with the piston head 13 by its connection to the piston rod14, thereby compressing the return spring 39. In this initial movementthe upper carriage 31 is connected to the lower carriage 32 to movetherewith as a unit through the magnet 44 and bar 46 connection. As thecarriages continue to move downwardly the wire 55 is compressed againstthe head 59 by the welding surface 56 of the electrode 54. Pressurethereby exerted upon the wire insulation, by way of example only of theorder 9 to 15 pounds, is sufficient to cold flow the insulation, therebymechanically separating it at the interfaces of the wire with both theelectrode surface 56 and the surface of the terminal pin head 59 to givea metal to metal connection through the electrodes, wire and terminalpin.

At maximum pressure the magnet 44 breaks free from the magnetic bar 46and the pull exerted on the upper carriage 31 and electrode 54immediately declines to that force which is exerted by theconstant-force spring 43 which, by way of example only, is of the orderof 2% pounds. At the bottom of its stroke, just prior to its engagementwith the top of the base 11, the bottom carriage 32 engages arm 26 andoperates switch 25 to actuate the welding power supply circuit. Thisenergizes the electrodes 22 and 54 through the lines 23 and 63, therebypassing a welding current through the wire 55 and the terminal pin head59 to weld them together. The amplitude and duration of the weldingcurrent is under control of the power supply in known manner.

When the weld is completed, the valve 16 is turned to release the air atthe top of the chamber 12 through the vent l7, whereupon return spring39 moves the lower carriage 32 upwardly to engage the magnet 44 with thebar 46 and move both carriages together upwardly until the uppercarriage 31 is stopped by the cross-bar 29 in the position of FIG. 1where it is ready to begin another welding operation.

If the optional dashpots 65 and-66 are used, they will stop anymechanical transient movements which may occur as the magnet 44separates from and engages the bar 46, to smooth out the movement of thecarriages.

With the use of a constant-force spring 43 between the carriages 31 and32, terminal pins 57 may have optionally long and short stems withoutmaking any adjustment in the mechanism as long as the stem permitsinsertion of the terminal pin between the electrodes. With theconstant-force spring 43 the length of travel of the upper carriage 31and the electrode 54 is immaterial since, whether this travel is shortor long, the constant-force spring 43 will exert the same weldingpressure between the wire and the terminal pin head without making anyadjustments to the welding machine mechanism.

FIG. 2 shows a portion only of the same mechanism as in FIG. 1 but witha change in the operating means for moving the lower carriage 32, fromthe pneumatic cylinder 12 of FIG. 1 to a cable operation in FIG. 2. Withall other parts remaining the same, a rod 71 is substituted for thepiston rod 14 and is connected to the lower carriage 32 in the same wayand has the return spring 39 therearound. A flexible cable 72 may be inthe form of a tachmometer style cable in which a cable wire is enclosedwithin a flexible sheath 73. This sheath is soldered or otherwiseconnected in an entrance throat 74 of an enclosure 75 depending from thebase 11. Within the enclosure 75 the end of the cable 72 is providedwith a tongue fitting 76 which is swiveled in a clevis 77 on the end ofthe rod 71. The opposite end of the cable 72 is pivotally connected toan arm 78 rigidly secured to a foot pedal 79 pivoted at 81 to a baseplate 82. As the pedal 79 is depressed it will pull on the cable 72 todraw the lower carriage 32 downwardly in the same manner as thepneumatic operator in FIG. 1. When the foot pedal 79 is released it willbe moved upwardly by the cable 72 as the carriage 32 moves upwardlyunder the action of the return spring 39.

In the modification of FIG. 3, the constant-force spring 43 hassubstituted therefore, a standard coiled extension spring 85 connectedbetween the bracket 61 and an arm 86 rigid with the lower carriage 32 bya pair of screw-eyes 87. The spring 85 has a constant so thatthe forceexerted thereby depends on the amount it is extended by separation ofthe carriages 31 and 32. A long set-screw 88 is threaded into the arm 86and has its end engaging an arm 89 extending from the base 11 to controlthe lower position of the carriage 32, thereby limiting its travel. Asecond set-screw 91 is threaded into the arm 86 and is adjusted toengage the operator of the switch 92 so that switch is operated justprior to the engagement of the setscrew 88 with the arm 89.

The insulation breakdown pressure in the modification of FIG. 3 isobtained the same as in FIG. 1 from the holding force of the magnet 44,this holding force being. adjustable by replacement of the magnet with astronger or weaker one. In the modification of FIG. 3 the length of thestem of the terminal pin cannot be varied without changing the weldingpressure since the length of the stern determines the separation betweenthe carriages 31 and 32, the amount of extension of the spring 85, andthe welding pressure. However, the modification of FIG. 3 allows thewelding pressure to be varied at will by controlling the amount ofextension of the spring 85 by adjustment of the set-screw 88 whichlimits the downward movement of the carriage 32. As the set-screw 88 isadjusted the set-screw 91 should also be adjusted to conform therewith.

While certain preferred embodiments of the invention have beenspecifically illustrated and described, it will be understood that theinvention is not limited thereto as many variations will be apparent tothose skilled in the art and the invention be given its broadestinterpretation within the terms of the following claims.

I claim:

1. A dual pressure welding machine comprising:

first and second electrodes;

a pair of moveable carriages;

said first electrode mounted on said first carriage for movementtherewith;

means for moving the other of said carriages;

means for making a magnetic connection between said carriages to connectthe carriages for movement together as a unit;

a spring interconnecting said carriages for action relative theretoafter the magnetic connection is broken; I

movement of said other carriage intially moving said carriages togetheras a unit until said first electrode engages a pair of elements to bewelded together, with the pressure between said electrode and saidelements thereby building up to a value at which said magneticconnection is broken;

the force thereafter on said firstcarriage and first electrode beingdetermined by the spring'connection between the carriages independentlyof the now open magnetic connection; and

means for energizing said electrodes to make the weld under the pressureexerted by the spring connection between said carriages.

2. The welding machine defined in claim 1, including:

a passage through one of said first and second electrodes;

I an insulated wire fed through said passage to loop past the weldingface of said one electrode; and

a terminal element to which said wire is to be welded, the initialpressureia'pplied by said magnetic connection being sufficient tomechanically separate the insulation at the interfaces between the wire,the one electrode surface and the terminal element to secure metal tometal contact thereat and said spring connection between said carriagesapplying a lower pressure desired between the wire and terminal elementfor the welding operation.

3. The welding machine defined in claim 1 in which said spring applies aconstant-force regardless of its extension so that terminals of variouslengths may 'be welded in the machine with constant welding pressurewithout change in the machine mechanism.

4. The welding machine defined in claim 1 in which said springconnecting the carriages is an extension spring with a constant so thatthe force exerted thereby depends upon its extended length; and

means for adjustably limiting the position of said other carriage so asto limit the extension of the spring and the welding pressure developedthereby.

5. The welding machine defined in claim 4 including:

means adjustable to determine the point in the travel of said othercarriage at which the electrodes are energized to pass current throughthe weld.

6. The welding machine defined in claim 1 including:

a pneumatic operator connected to said other carriage for effectingmovement thereof in one direction; and

a return spring for effecting movement of said other carriage in theopposite direction. I

7. The welding machine defined in claim 1 including:

a foot pedal;

a flexible cable interconnecting said foot pedal and said other carriagefor affecting movement thereof in one direction; and

a return spring for affecting movement of said other carriage in theopposite direction.

8. The welding machine defined in claim 1 including:

a base;

means mounting a pair of shafts on said base in parallel,

spaced relation; and

bushings on said carriages receiving said shafts for slidably mountingsaid carriages thereon for movement parallel the axes thereof.

9. The welding machine defined in claim 8 in which said bushings are ofthe longitudinally recirculating, ball-type for minimizing frictionalresistance to movement of the carriages.

10. The welding machine defined in claim 1 including:

dashpot means connected to said carriages for damping mechanicaltransients which may occur when the magnetic connection is broken andmade. I

11. The welding machine defined in claim 10 in which there is onedashpot means interconnecting said carriages and the second dashpotmeans interconnecting said other carriage and a fixed part.

12. The welding machine defined in claim 1 including:

a fixedly mounted control switch for the power supply to the saidelectrodes; and

an operator for said switch engaged by said other carriage to operatethe switch just prior to the limit of travel of said other carriage inthe welding direction.

13. A dual pressure welding machine comprising:

stationary and moveable electrodes adapted to efiect a weldingoperationtherebetween; a moveable member; means for making a magnetic connectionbetween said moveable member and said moveable electrode whereby saidmoveable member and moveable electrode are connected together toinitially move together as-a unit to apply a first relatively higherpressure between said electrodes, said magnetic connection breaking at apre-determined pressure value; and t spring means interconnecting saidmoveable member and moveable electrode to exert a second relativelylower pressure between said electrodes after said magnetic connection isbroken to apply a welding pressure for the welding operation. 14. Thewelding machine defined in claim 13 in which said spring means applies aconstant-force regardless of its extension whereby the welding pressureremains constant regardless of the amount of separation between saidmoveable member and moveable electrode.

15. The welding machine defined in claim 13 including: means to feed aninsulated wire between said electrodes which is to be welded inconducting relation to a terminal P said first pressure exerted throughsaid magnetic connection being sufiicient to mechanically separate theinsulation from said wire at its interfaces with one of said electrodesand the terminal part to which it is to be welded.

16. The welding machine defined in claim 1, including:

means for supporting an insulated wire for welding thereof, saidsupporting means including a passage through one of said first andsecond electrodes through which said wire is fed to loop past thewelding face of said one electrode.

17. The welding machine defined in claim 16 in which said one electrodeis said first electrode.

18. The welding machine defined in claim l in which said secondelectrode is a stationary electrode positioned in line with said firstelectrode; and I means for supporting said elements between said'firstand second electrodes for welding therebetween.

19. The welding machine defined in claim 18 in which said supportingmeans for said elements includes said second electrode.

20. The welding machine defined in claim 18, including:

a passage through one of said first and second electrodes;

an insulated wire fed through said passage to loop past the welding faceof said one electrode; and

a terminal element to which said wire is to be welded disposed betweensaid electrodes, the initial pressure applied by said magneticconnection being sufficient to mechanically separate the insulation atthe interfaces between the wire, the one electrode surface and theterminal element to secure metal to metal contact thereat, and saidspring connection between said carriages applying a lower pressuredesired between the wire and terminal element for the welding operation.

21. A dual pressure welding machine comprising:

means for supporting a workpiece to be welded;

means for positioning a conductor adjacent said workpiece for weldingthereto;

first and second electrodes adapted to respectively contact saidconductor and said workpiece to effect a welding operation therebetween;

a moveable member;

means for making a magnetic connection between said moveable member andsaid first electrode whereby they are connected together and initiallymove together to sion whereby the welding pressure remains constantregardless of the amount of separation between said moveable member andsaid first electrode.

23. The welding machine defined in claim 21 in which: said conductor isan insulated conductor; and said first relatively higher pressureexerted through said magnetic connection being sufficient tomechanically separate the insulation from said conductor at itsinterfaces with said first electrode and said workpiece to which it isto be welded.

l i F i

1. A dual pressure welding machine comprising: first and secondelectrodes; a pair of moveable carriages; said first electrode mountedon said first carriage for movement therewith; means for moving theother of said carriages; means for making a magnetic connection betweensaid carriages to connect the carriages for movement together as a unit;a spring interconnecting said carriages for action relative theretoafter the magnetic connection is broken; movement of said other carriageintially moving said carriages together as a unit until said firstelectrode engages a pair of elements to be welded together, with thepressure between said electrode and said elements thereby building up toa value at which said magnetic connection is broken; the forcethereafter on said first carriage and first electrode being determinedby the spring connection between the carriages independently of the nowopen magnetic connection; and means for energizing said electrodes tomake the weld under the pressure exerted by the spring connectionbetween said carriages.
 2. The welding machine defined in claim 1,including: a passage through one of said first and second electrodes; aninsulated wire fed through said passage to loop past the welding face ofsaid one electrode; and a terminal element to which said wire is to bewelded, the initial pressure applied by said magnetic connection beingsufficient to mechanically separate the insulation at the interfacesbetween the wire, the one electrode surface and the terminal element tosecure metal to metal contact thereat , and said spring connectionbetween said carriages applying a lower pressure desired between thewire and terminal element for the welding operation.
 3. The weldingmachine defined in claim 1 in which said spring applies a constant-forceregardless of its extension so that terminals of various lengths may bewelded in the machine with constant welding pressure without change inthe machine mechanism.
 4. The welding machine defined in claim 1 inwhich said spring connecting the carriages is an extension spring with aconstant so that the force exerted thereby depends upon its extendedlength; and means for adjustably limiting the position of said othercarriage so as to limit the extension of the spring and the weldingpressure developed thereby.
 5. The welding machine defined in claim 4including: means adjustable to determine the point in the travel of saidother carriage at which the electrodes are energized to pass currentthrough the weld.
 6. The welding machine defined in claim 1 including: apneumatic operator connected to said other carriage for effectingmovement thereof in one direction; and a return spring for effectingmovement of said other carriage in the opposite direction.
 7. Thewelding machine defined in claim 1 including: a foot pedal; a flexiblecable interconnecting said foot pedal and said other carriage foraffecting movement thereof in one direction; and a return spring foraffecting movement of said other carriage in the opposite direction. 8.The welding machine defined in claim 1 including: a base; means mountinga pair of shafts on said base in parallel, spaced relation; and bushingson said carriages receiving said shafts for slidably mounting saidcarriages thereon for movement parallel the axes thereof.
 9. The weldingmachine defined in claim 8 in which said bushings are of thelongitudinally recirculating, ball-type for minimizing frictionalresistance to movement of the carriages.
 10. The welding machine definedin claim 1 including: dashpot means connected to said carriages fordamping mechanical transients which may occur when the magneticconnection is broken and made.
 11. The welding machine defined in claim10 in which there is one dashpot means interconnecting said carriagesand the second dashpot means interconnecting said other carriage and afixed part.
 12. The welding machine defined in claim 1 including: afixedly mounted control switch for the power supply to the saidelectrodes; and an operator for said switch engaged by said othercarriage to operate the switch just prior to the limit of travel of saidother carriage in the welding direction.
 13. A dual pressure weldingmachine comprising: stationary and moveable electrodes adapted to effecta welding operation therebetween; a moveable member; means for making amagnetic connection between said moveable member and said moveableelectrode whereby said moveable member and moveable electrode areconnected together to initially move together as a unit to apply a firstrelatively higher pressure between said electrodes, said magneticconnection breaking at a pre-determined pressure value; and spring meansinterconnecting said moveable member and moveable electrode to exert asecond relatively lower pressure between said electrodes after saidmagnetic connection is broken to apply a welding pressure for thewelding operation.
 14. The welding machine defined in claim 13 in whichsaid spring means applies a constant-force regardless of its extensionwhereby the welding pressure remains constant regardless of the amountof separation between said moveable member and moveable electrode. 15.The welding machine defined in claim 13 including: means to feed aninsulated wire between said electrodes which is to be welded inconducting relation to a terminal part; said first pressure exertedthrough said magnetic connection being sufficient to mechanicallyseparate the insulation from said wire at its interfaces with one ofsaid electrodes and the terminal part to which it is to be welded. 16.The welding machine defined in claim 1, including: means for supportingan insulated wire for welding thereof, said supporting means including apassage through one of said first and second electrodes through whichsaid wire is fed to loop past the welding face of said one electrode.17. The welding machine defined in claim 16 in which said one electrodeis said first electrode.
 18. The welding machine defined in claim 1 inwhich said second electrode is a stationary electrode positioned in linewith said first electrode; and means for supporting said elementsbetween said first and second electrodes for welding therebetween. 19.The welding machine defined in claim 18 in which said supporting meansfor said elements includes said second electrode.
 20. The weldingmachine defined in claim 18, including: a passage through one of saidfirst and second electrodes; an insulated wire fed through said passageto loop past the welding face of said one electrode; and a terminalelement to which said wire is to be welded disposed between saidelectrodes, the initial pressure applied by said magnetic connectionbeing sufficient to mechanically separate the insulation at theinterfaces between the wire, the one electrode surface and the terminalelement to secure metal to metal contact thereat, and said springconnection between said carriages applying a lower pressure desiredbetween the wire and terminal element for the welding operation.
 21. Adual pressure welding machine comprising: means for supporting aworkpiece to be welded; means for positioning a conductor adjacent saidworkpiece for welding thereto; first and second electrodes adapted torespectively contact said conductor and said workpiece to effect awelding operation therebetween; a moveable member; means for making amagnetic connection between said moveable member and said firstelectrode whereby they are connected together and initially movetogether to apply a first relatively higher pressure between said firstelectrode and said conductor, said magnetic connection breaking at apredetermined value; spring means interconnecting said moveable memberand said first electrode to exert a second and relatively lower pressurebetween said first electrode and said conductor after said magneticconnection is broken; and means for applying a welding current to saidelectrodes to effect said welding operation at said relatively lowerpressure.
 22. The welding machine defined in claim 21 in which saidspring means applies a constant-force regardless of its extensionwhereby the welding pressure remains constant regardless of the amountof separation between said moveable member and said first electrode. 23.The welding machine defined in claim 21 in which: said conductor is aninsulated conductor; and said first relatively higher pressure exertedthrough said magnetic connection being sufficient to mechanicallyseparate the insulation from said conductor at its interfaces with saidfirst electrode and said workpiece to which it is to be welded.